In recent years, in order to prove the accuracy of forming a pneumatic tire, a tire manufacturing method using a rigid inner old is proposed. The manufacturing method of this kind, for example, comprises a step of forming a green tire and a vulcanization step of vulcanizing the green tire on the rigid inner mold on an outer surface of the rigid inner mold.
The rigid inner mold comprises an inner mold body and a core. The inner mold body comprises a plurality of segments. Upon the assembly of the segments, the inner mold body is formed in an annular shape having a central hole. Since the core is disposed in the central hole of the inner mold body, the respective segments are substantially constrained. Thus, the inner mold body may be held in the annular shape by the core.
The segments comprise first segments and second segments, and they are arranged alternately in the tire circumferential direction. Each of the first segments is provided at both ends in a tire circumferential direction with division surfaces inclined radially inward in a direction in which a circumferential length decreases. Each of the second segments is provided in the tire circumferential direction with division surfaces inclined radially inward in a direction in which a circumferential length increases. Such plurality of segments may be removed from an inner cavity of the tire by being moved radially inward of the tire sequentially from the second segments.
The first segments and the second segments are moved radially outward of the tire thereby increasing respective gaps between the first segments and the second segments. Further, since each of the first segments and each of the second segments are moved radially inward of the tire, the adjacent segments are in contact. Owing to such a contact between the adjacent segments, the first segment is pushed radially outward of the tire along an inclination of the division surface of the second segment, thereby increasing a level difference of the outer surface between the segments.    Patent Document 1: JP Patent Publication No. 2013-6367